A substantial body of research has established the effectiveness of brief interventions (BI) for hazardous alcohol use in patients seen in medical settings, prompting the implementation of dissemination projects of screening and brief intervention for "substance abuse" on a widespread scale. However, there are few studies examining the efficacy of BI for problem drug use and abuse in medical settings, and there is considerable variability in what actually constitutes a BI (i.e., what are the important or active therapeutic ingredients). The potential costs related to untreated drug abuse in medical settings are substantial. Although there is great human suffering and morbidity for the abuser, it is likely that potential healthcare cost savings and decreased adverse healthcare outcomes related to BI will be the major drivers of policy change to improve provision of BI treatment. Accordingly, this application proposes to conduct a policy-relevant clinical trial with broad external validity (a hybrid "efficacy-effectiveness" study) informed by the literature on BI and alcohol use, to evaluate the efficacy of BI and referral to treatment when indicated, in patients with problem drug use and abuse seen in the primary care medical setting at a large safety-net hospital. The study has four aims: (1) to determine if BI is effective in reducing drug use and increasing completed referral to treatment (i.e., treatment initiation);(2) to test whether higher fidelity to a BI model that emphasizes motivational interviewing is more effective than lower fidelity;(3) to estimate the impact of BI on several public health outcomes;(4) to estimate the costs of the intervention, potential cost offsets, and incremental cost-effectiveness from the payer perspective based on health care service use and drug use frequency. PUBLIC HEALTH RELEVANCE: This project is evaluating the effectiveness of an intervention that has recently been approved as a billable service in the medical care setting, despite the absence of data supporting its use in drug abuse and dependence. The results of the study will have implications for whether it is advisable to expand its application beyond hazardous alcohol abuse to include abuse of drugs.